Process of making permeable ceramic products



Patented Nov. '7, 1933 l UNITED STATES PATENT OFFICE PROCESS OF MAKING PERMEABLE CERAMIC PRODUCTS William L. Stafford, Somerville, N. 5., assignor to Johns-Manville Corporation, New York, N. Y., a corporation of New York No Drawing. Application May 21, 1931 Serial No. 539,138

Claims. (0]. -156) The present invention relates to the manu- The argillaceous body material or clay sefacture of porous products by the removal of adlected should be fairly plastic and preferably mixed solid particles and particularly to the manburn to a white or buff color, also various color ufacture of porous ceramic articles by the sepastains may be incorporated if desired. The dry 5 ration by volatilization of naphthalene or similar modulus of rupture of such clay should be not material added to the raw ceramic mix. less than 100 lbs. per sq. in., and the modulus The invention is particularly directed to the of rupture after firing at say 2250* F. should be provision of a porous or permeable tile having above 2000 lbs. per sq. in. The pyrometric cone numerous intercommunicating poreswhich open equivalent should be above cone 20 (2775 F.).

10 to the surface of the tile. A sponge-like struc- The linear fired shrinkage at 2250 F. should prefture of this character adapts the tile especially erably be lower than 20%. This type clay or a well for use for acoustical purposes. blend of clays having such properties are well The manufacture of porous ceramic articles by known in the ceramic art, as for example plastic mixing naphthalene with the raw ceramic mix, fireclays, but it will be appreciated that plastic 1 molding the mixture, and thereafter producing high shrinking clays as ball clays can be used if voids in the molded article by subliming or evapgrog is added, that more refractory clays of crating the naphthalene therefrom, is described higher maturing temperature such as kaolins can in German Patent #2334? to Stein. be used if the firing temperature is proportionally It has been found however, that the process of raised, or that less refractory clays as common 20 this patent is not satisfactory due to the fact brick clays may be used if the firing temperature that during the heating stage for the removal of is proportionately reduced. the naphthalene by evaporation the molded The naphthalene should preferably be in the product tends to become very plastic and deforms shape of rounded particles which pass through an under its own weight due to the fluid character 18 mesh screen, altho angular particles of flaky 25 of the melted naphthalene. Slow removal of the naphthalene crystals may alternately be used of naphthalene by sublimation alone, an alternative a size best suited to secure certain attractive procedure disclosed by this patent is also objecarchitectural effects, as for example, combinationable due to the very long period of time retions of large irregular flakes with small round quired. These disadvantages are especially great pellets or all angular 'grains of less than 8 mesh 30 in the manufacture of a product having relatively prepared by grinding and screening caked naphgreat permeability such as is requisite in an thalene. The roundednaphthalene of less than acoustical tile due to the necessity of employing 18 mesh screen size may readily be secured by large amounts of naphthalene. melting the crystals recovered from the drying The principal object of this invention is the operation, and atomizing the resulting liquid by 35 provision of a method and article whereby these hitting a stream of the molten material with disadvantages may be obviated. It has been discompressed air, and blowing it into an enclosed covered that this object may be attained by inchamber where it drops in the form of minute corporating a relatively small amount of cemenspheres. The naphthalene content should not titious material in the raw mix together with the be over 75% by weight of the total batch as 40 naphthalene or similar material. The cementimore than this gives excessiveweakness' Any tious material or bonding agent thus used must lesser quantity may be 'used dependent upon the have'characteristics which adapt it to set or bind porosity desired. and impart sumcient strength to the molded mix- The cementitious material may be calcined ture to prevent deformation during the heating gypsum, Incor cement, lumnite cement or Port- 45 stage wherein the naphthalene or equivalent maland cement, or any form of hydraulic setting 1 0 terial is melted and volatilized. Calcined gypsum agent with similar properties. Calcined gypsum and various other varieties of hydraulic setting is preferred because of its lower cost altho quick cements have been ascertained to have the reqsetting Portland (Incor) is an entirely satisfactory uisite properties. substitute otherwise. Other forms of bonding 50 For the purpose of example, and merely to or reenforcing materials such as bentonite may illustrate one way of practicing the invention, in be utilized to produceceramic mixes which will the preferred process for the manufacture of a not deform during the heating step incident to porous, permeable tile for acoustical correction the removalof the naphthalene. The amount of purposes, the base materials and process may be such material may vary from 5 to 30% of the 55 cs follows: weight of clay. It may be generally stated that By weight Clay (as above) 28 Naphthalene (thru 18 mesh) 65 Calcined gyps m '7 Other ways of forming the shape will occur to one skilled in the art, as for example by extruding from an auger machine, slop-molding and repressing, or casting into molds. The formed tile may be handled directly into a drier operating at 212 F. or any temperature in excess of 176 F. but below the spontaneous combustion point of naphthalene (above 425 F., vaporizing point). The naphthalene and water vapor are removed by fan from the drying chamber into a cool chamber and the naphthalene condenses out and is thus recovered for reuse.

The dry tile may then be set directly in a suitable kiln for firing to a temperature of 2300 F.

' This temperature is satisfactory for the preferred composition, and gives 9% linear shrinkage. After cooling, a face may be ground down to remove any surface skin effect and to expose more fully the interconnecting pores. It is apparent that interconnecting pores are a corallary of the process, as the removal of the naphthalene in fluid and vapor state necessarily creates intercommunication. This may be enhanced by various means such as by using rounded particles of naphthalene of a size giving maximum contiguity, and by firing to certain temperatures which experiment shows gives maxium break down of the clay film between voids.

Using the above described composition and procedure, buff colored acoustical tilehave been produced in quantity with a density of 26 lbs. per cu. ft.; a modulus of rupture of 75 to 100 lbs. per sq. inch; a porosity of 85%; a specific permeability of 0.98 c. 0. per sec. per cm per cm. thick per cm. H2O pressure, and a sound absorption efficiency at 256 cycles frequency of 48%.

It is apparent that other porous shapes may be made by the same process, as for example, in-- sulating brick or block. The shapes may be easily sawed or nailed, and applied to exterior wall surfaces when employed for acoustical use with plaster or various adhesives. Minor variations in the amount, shape and size of naphthalene, and its relative distribution in the piece, in the kind of clays or ceramic body compositions, in the amount and kind of cementitious material used,-

and in the firing temperature employed, are all possible so that close control of the final properties is possible in order to meet any particular set of conditions for a porous ceramic article.

Various materials may be substituted for naphthalene in the practice of my invention such as anthracene or even inorganic material. The material used for this purpose should preferably be liquefiable and readily volatilized and also water-insoluble in order that it will not dissolve in the raw mix. In some instances the admixed solid may be removed by merely melting it and draining it from the molded mixture; Under this condition the cementitious material functions to prevent deformation during the heating step as before. Substances such as paraflin or even naphthalene lend themselves to treatment by this method. As indicated any amount of the volatile solid may be employed but for acoustical purposes the quantity added should be sufilcient to impart suflicient permeability so that the final product will absorb at least 35% of the sound having a frequency of 500 cycles impinging on its exposed surface.

What I claim is: i

1. A process of manufacturing porous structural shapes such as bricks, slabs and the like which comprises admixing a body material having relatively small bonding strength, a volatile solid, and a cementitious material capable of hardening at a relatively low temperature and imparting sufiicient strength to the admixture to prevent substantial disintegration or deformation thereof during the subsequent heating stage, forming the mixture into suitable shapes, and heating the shaped mass to volatilize the volatile solid.

2. A'process of manufacturing porous structural shapes such as bricks, slabs and the like which comprises admixing a body material having relatively small bonding strength at low temperatures but capable of developing a strong ceramic bond at elevated temperatures, a volatile solid, and a cementitious material capable of hardening at a relatively low temperature and imparting sufiicient strength to the'admixture to prevent substantial disintegration or deformation thereof during the subsequent heating stage, forming themixture into suitable shapes, heating the shaped mass to volatilize the volatile solid, and then further heating the porous mass until the body material is ceramically bonded.

3. A proces of manufacturing porous structural shapes such as bricks, slabs and the like which comprises admixing an argillaceous body material having relatively small bonding strength a volatile solid and a cementitious material capable of hardening at a relatively low temperature and imparting sufiicient strength to the admixture to prevent substantial disintegration or def ormation thereof during the subsequent heating stage, forming the mixture into suitable shapes, and heating the shaped mass to volatilize the volatile solid and then-further heating the porous mass to develop a ceramic bond in the argillaceous body material. v

4. A process of manufacturing porous structural shapes such as bricks, slabsand the like which comprises admixing a plastic clay having a relatively low drying shrinkage, a volatile solid,

and a cementitious material capable of hardening at a relatively low temperature and impart-' ing sufllcient strength to the admixture to pre- "vent substantial disintegration or deformation thereof during the subsequent heating stage,

forming the mixture into suitable shapes, and

heating the shaped mass to volatilize the volatile solid and then further heating the resultant porous mass to develop a ceramic bond inthe plastic clay material.

forming the mixture into suitable shapes, andheating the shaped mass to a temperature sufi'iciently high to melt and volatilize the volatile solid.

6. A process of manufacturing porous structural shapes such as bricks, slabs and the like which comprises admixing a body material having relatively small bonding strength, a water insoluble volatile solid, and a cementitious material capable of hardening at a relatively low temperature and imparting sufiicient strength to the admixture to prevent substantial disintegration or deformation thereof during the subsequent heating state, forming the mixture into suitable shapes, and heating the shaped mass at a temperature sufiiciently high to melt and volatilize the volatile solid.

7. A process of manufacturing porous structural shapes such as bricks, slabs and the like which comprises admixing a body material having relatively small bonding strength at low temperatures, naphthalene and a cementitious material capable of hardening at a relatively low temperature and imparting suflicient strength to the admixture to prevent substantial disintegration or deformation thereof during the subsequent heating stage, forming the mixture into suitable shapes, and heating the shaped mass to volatilize the naphthalene.

8. A process of manufacturing porous, structural shapes such as bricks, slabs and the like which comprises admixing a body material having relatively small bonding strength, a solid having a low melting point, and a hydraulic cement material capable of setting and hardening at substantially atmospheric temperature and imparting suflicient strength to the admixture to prevent substantial disintegration or deformation thereof during the subsequent heating stage, forming the mixture into suitable shapes, and heating the shaped mass to melt the solid having the low melting point and separating the liquid from the shaped mixture.

9. A process of manufacturing porous molded shapes of light weight porous ceramic material which comprises forming a plastic or fluid mass of clay, a volatile readily liquefiable solid, and a cementitious material, forming the mass into the desired shapes, permitting the cementitious material to set and impart suflicient strength to the shaped mass to prevent substantial deformation thereof during the subsequent heating stage wherein the said volatile solid is liquefied, and then heating the shaped mass to a sufficient temperature to liquefy the volatile material and separate it from the mass by volatilization, further heating the porous mass thus produced to impart a ceramic bond thereto.

10. A process of manufacturing porous molded shapes of light weight porous ceramic material which comprises forming a plastic or fluid mass of clay, naphthalene and a cementitious material, forming the mass into the desired shapes, permitting the cementitious material to set and impart sufficient strength to the shaped mass to prevent substantial deformation thereof during the subsequent heating stage wherein the said volatile solid is liquefied and then heating the shaped mass to a sufficient temperature to liquefy the volatile material and separate it from the mass by volatilization, further heating the porous mass thus produced to impart a ceramic bond thereto.

11. A process of manufacturing porous molded shapes of light weight porous ceramic material which comprises forming a plastic or fluid mass of clay, a volatile liquefiable solid and a hydraulic cement, forming the mass into the desired shapes, permitting the cementitious material to set and impart suflicient strength to the shaped mass to prevent substantial deformation thereof during the subsequent heating stage wherein the said volatile solid is liquefied, and then heating the shaped mass to a suflicient temperature to liquefy the volatile material and separate it from the mass by volatilization, further heating the porous mass thus produced to impart a ceramic bond thereto.

12. A process of manufacturing porous molded shapes of light weight porous ceramic material which comprises forming a plastic or fluid mass of clay, a volatile liquefiable solid and a quicksetting hydraulic cement, forming the mass into the desired shapes, permitting the cementitious I material to set and impart suilicient strength to the shaped mass to prevent substantial deforma-' tion thereof during the subsequent heating stage wherein the said volatile solid is liquefied and then heating the shaped mass to a sufficient temperature to liquefy the volatile material and separate it from the mass by volatilization, further heating the porous mass thus produced to impart a ceramic bond thereto.

13. A shaped mass comprising a body material having little bonding strength, a relatively small amount of cementitious material intermixed with the body material and imparting sufficient strength to the mass to maintain its structure,

said mass comprising a multiplicity of pores constituted by voids left in the mass by removal of solid matter initially admixed therewith.

14. A shaped mass comprising a ceramic body material having little bonding strength, a relatively small amount of cementitious material intermixed with the body material and imparting sufficient strength to the mass to maintain its structure, said mass comprising a multiplicity of pores constituted by voids left in the mass by removal of solid matter initially admixed therewith.

15. A shaped mass comprising a body material having little bonding strength, a relatively small amount of cementitious material intermixed with the body material and imparting sufficient strength to the mass to maintain its structure, said mass comprising a multiplicity of pores constituted by voids left in the mass by lique-a faction and volatilization of a volatile liquefiable solid material initially admixed therewith.

WILLIAM L. STAFFORD. 

